1. Field of the Invention
The present invention relates to indicators and/or display units and more particularly to electronic MFDI (multifunctional digital indicators) or displays such as event counters or elapsed time indicators and the like which can preserve the status of the time or event display even in the event of a complete power loss for an indefinite period of time.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
There are numerous situations where the amount of time or elapsed time a machine or process runs may be of critical importance. The running time of a jet engine is one specific example. Likewise, there are numerous situations where the number of occurrences of a particular event or activity may also be important if not critical. However, the events may occur over a long period of time such as months or even years with complete unpredictability. Similarly, the running of the machine or process may start and stop at unpredictable times over lengthy periods. Consequently, it is important to be able to record the occurrence and/or amount of such unpredictable events and/or running time automatically and without having to maintain one or more individuals at the necessary locations to monitor and manually record such occurrences and running times.
In the past, events or elapsed time indicators which operated automatically without a human attendant, and which could maintain their status even in the event of complete loss of electrical power were typically mechanical clock-like devices or hybrid devices which included a significant amount of precision machining and provided mechanical-type displays which were electrically driven and electronically controlled. Excellent examples of such prior art devices are manufactured by Electrodynamics, Inc. in Rolling Meadows, Ill., the assignee of the present invention under the product name Dynatime.RTM.. Although such mechanical or hybrid devices provide excellent performance and dependability, such devices include a significant amount of precision clock-like machining which is expensive to produce and may be susceptible to damage by harsh environment and handling conditions.
Unfortunately, such devices having such a high content of precision manufacturing typically require substantially different designs for counting events and/or recording elapsed time. Further, such mechanical devices may also have high electrical power requirements.